TitleEvolutionary origins of the vertebrate heart: Specification of the cardiac lineage in Ciona intestinalis.
Publication TypeJournal Article
Year of Publication2003
AuthorsDavidson, B, Levine, M
JournalProc Natl Acad Sci U S A
Date Published2003 Sep 30
KeywordsAnimals, Base Sequence, Biological Evolution, Cell Lineage, Ciona intestinalis, DNA Primers, Myocardium

Here we exploit the extensive cell lineage information and streamlined genome of the ascidian, Ciona intestinalis, to investigate heart development in a basal chordate. Several cardiac genes were analyzed, including the sole Ciona ortholog of the Drosophila tinman gene, and tissue-specific enhancers were isolated for some of the genes. Conserved sequence motifs within these enhancers facilitated the isolation of a heart enhancer for the Ciona Hand-like gene. Altogether, these studies provide a regulatory framework for the differentiation of the cardiac mesoderm, beginning at the 110-cell stage, and extending through the fusion of cardiac progenitors during tail elongation. The cardiac lineage shares a common origin with the germ line, and zygotic transcription is first detected in the heart progenitors only after its separation from the germ line at the 64-cell stage. We propose that germ-line determinants influence the specification of the cardiac mesoderm, both by inhibiting inductive signals required for the development of noncardiac mesoderm lineages, and by providing a localized source of Wnt-5 and other signals required for heart development. We discuss the possibility that the germ line also influences the specification of the vertebrate heart.

Alternate JournalProc. Natl. Acad. Sci. U.S.A.